Strain relief for electrical connectors

ABSTRACT

Strain relief for electrical connectors in which a tubular member is moved into one end portion of a shell to force compressible means into tight engagement with a cable. The compressible means includes a C-shaped metal member of curved cross-sectional shape providing a rounded convex outer surface for wedge engagement with a frustoconical inner surface of the tubular member and further includes an annular member of elastomeric material having an internal surface forced into pressure engagement with the cable when axially compressed between one end of the tubular member and an internal shoulder of the shell.

United States Patent [72] inventor Wolfgang Hilbert Holzkirchen, Germany [21] App]. No. 4,002 [22] Filed Jan. 19, 1970 [45] Patented Nov. 16, 1971 [73] Assignee The Bunker-Ramo Corporation Oak Brook, Ill.

[54] STRAIN RELIEF FOR ELECTRICAL CONNECTORS 3 Claims, 3 Drawing Figs.

[52] US. Cl 339/103, 339/177 [51] Int. Cl ll0lr 13/58 [50] Field of Search 339/177, 143, 268, 103 T; 285/340 [56] References Cited UNITED STATES PATENTS 2,023,823 12/1935 Ruger 339/268 2,995,388 8/1961 Morrello, Jr. et al. 285/340 3,275,737 9/1966 Caller 339/103 X 3,292,136 12/1966 Somerset 339/103 X 3,432,798 3/1969 Brishka 339/177 X Primary Examiner-Richard E. Moore Attorney-Frederick M. Arbuckle ABSTRACT: Strain relief for electrical connectors in which a tubular member is moved into one end portion of a shell to force compressible means into tight engagement with a cable. The compressible means includes a C-shaped metal member of curved cross-sectional shape providing a rounded convex outer surface for wedge engagement with a frustoconical inner surface of the tubular member and further includes an annular member of elastomeric material having an internal surface forced into pressure engagement with the cable when axially compressed between one end of the tubular member and an internal shoulder of the shell.

PATENTEDNUV 161971 NW mw bw 1 IHIHHHHHIHIIH WT, mm 0 STRAIN RELIEF FOR ELECTRICAL CONNECTORS This invention relates to a strain relief for electrical connectors and more particularly to a highly reliable strain relief in which a cable is readily installed and securely held against axial displacement.

Strain relief arrangements designed to prevent cables from being pulled out of electrical connectors are known in the art but have been relatively complicated in construction, have not been easy to install and have not always been reliable.

This invention was evolved with the general object of overcoming disadvantages of prior art strain relief arrangements and of providing a strain relief which is relatively simple in construction and economically manufacturable while being readily installed and very rugged, durable and reliable. According to this invention, a tubular member is arranged to be moved into one end portion of a shell to force compressible means into tight engagement with a cable within the shell.

According to an important feature of the invention, the compressible means comprises a generally C-shaped resilient metal member and the tubular member has an internal surface of generally frustoconical shape arranged to wedge the C- shaped member inwardly into tight engagement with the cable within the shell. Preferably, the C-shaped member has a curved cross-sectional shape to provide a rounded convex outer surface engageable by the internal surface of the tubular member and to also provide a pair of relatively sharp side edges arranged to bite into the cable at axially spaced points.

In accordance with another important feature, the compressible means comprises an annular member of elastomeric material arranged to be axially compressed between a shoulder within the shell and an inner end of the tubular member so as to case the inner surface of the annular member to be forced radially into tight engagement with the cable. Preferably, the annular member has an annular recess in the outer surface thereof effective to cause the inner surface thereof to be bowed radially inwardly when compressed axially. An annular metal member of generally L-shaped cross section is provided on one side of the annular member of elastomeric material, to contain the annular member while applying compressive forces thereto.

Either the C-shaped resilient metal member of the annular member of elastomeric material might be used alone but with a combination thereof, a very rugged and reliable connection is obtained to prevent axial displacement of the cable within the shell.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate a preferred embodiment and in which:

F IG. 1 is an expanded view of an electrical connector incorporating a strain relief according to the principles of this invention, showing the parts before assembly;

FIG. 2 is a view partly in cross section showing an assembled connector; and

FIG. 3 is a perspective view of a C-shaped member of the connector.

Reference numeral generally designates an electrical connector incorporating a strain relief constructed in accordance with the principles of this invention. The connector 10 comprises a main connector shell 11 within which contacts are supported in an insulating body for connection to mating contacts of another connector shell, not shown. An auxiliary shell 12 is provided arranged to be secured to the main shell 11 by means of a coupling ring 13 having an internally threaded portion 14 which is threaded on an externally threaded portion 15 of the shell 11. The coupling ring 13 is held on the shell 12 by means of a snapring l6 engaged in annular grooves in the outer surface of the shell 12 and in the inner surface of the coupling ring 13, the coupling ring 13 being rotatable relative to the shell 12.

An annular groove 17 is provided on the inside surface of the shell 12, adjacent the end thereof connected to the shell 1 i, for receiving a conventional O-ring seal member 18 which is compressed against an outer surface portion of the shell 11. To prevent relative rotation of the shells 11 and 12, the internal surface of the shell 12, between the end thereof and the notch 17, is fonned with equi-angularly spaced notches 19 which receive equi-angularly spaced projections 20 on the portion of the outer surface of shell 11 which is adjacent the threaded portion 15. A knurled disc 21 is provided at the end of shell 1 1.

A tubular member 22 is arranged to be moved into an op posite end portion 23 of the shell 12 and to force two forms of compressible means into tight engagement with the outer surface of an end portion of a cable 24 positioned within the shell 12. One of such compressible means comprises an annular member 25 of elastomeric material, such as a relatively soft natural rubber or an equivalent material, which is axially compressed between an internal annular shoulder 26 of the shell 12 and an inner end surface 27 of the tubular member 22. An annular metal member 28 is provided of generally L-shaped cross section having a first wall 29 between an end surface of the member 25 and the end surface 27 of the member 22 and having a second wall 30 surrounding an end portion of the member 25.

The second form of compressible means comprises a generally C-shaped resilient metal member 34 which is engaged by an internal surface 35 of the member 22 of generally frustoconical shape to wedge the member 34 inwardly into tight engagement with the cable 24, when the member 22 is moved into the end portion 23 of the shell 12. The C-shaped member 34 preferably has a curved cross-sectional shape to provide a rounded convex outer surface 36 engageable by the surface 35 and to provide a pair of relatively sharp side edges 37 and 38 arranged to bite into the cable at axially spaced points.

According to a further feature, the tubular member 22 has an externally threaded portion 39 which is threaded into an internally threaded portion 40 of the end portion 23 of shell 12.

The illustrated connector 10 is designed for use with a cable having an outer sheath of woven metal or the like and to receive and ground the sheath, a member 42 is provided having a wall 43 positioned between the inner end of the shell 11 and a shoulder 44 on the inside of the shell 12. The member 42 has a generally cylindrical wall into which axially extending slots are cut to form four relatively resilient fingers 45 which preferably have inwardly turned terminal end portions 46. 1

In the assembly of the connector, the shell 12, and members 22,25,28,34 and 42 are slid onto the end of the cable 24, in relative positions as shown in FIG. 1, and an outer sheath 47 of the cable 24, preferably of a woven metal material with an outer jacket 47a of a tough plastic material or the like, is expanded at one end of the cable and slipped onto the outside of the member 42, around the fingers 45, the outer jacket 470 being removed from the position of the sheath 47 around the fingers 45. The ends of wires 48 within the cable 24 are stripped of insulation and connected to contacts, not shown,; within the connector 10 and any wires or contacts to be grounded may be connected to a terminal 49 on the member 42. The shell 12 is then moved toward the shell 11 and the ring 13 is threaded onto the threaded portion 15 of the shell 11.

The sheath is engaged between the resilient fingers 45 and an v internal smoothly rounded surface 511 of the shell 12.

Next, the annular member 25 of elastomeric material together with the metal member 28 are moved within the end portion 23 of the shell 12 and the member 34 is moved to abut the wall 28 of the member 27. Finally, the tubular member 22 is threaded into place within the end portion 23 of the shell 12, as shown in FIG. 2, which serves to axially compress the member 25 and to force the inner surface thereof into tight sealing engagement with the outer surface of the outer jacket 47a. At the same time, the member 34 is wedged by the surface 35 into tight engagement with the outer jacket 470, with biting engagement between the edges 37 and 38 and the outer jacket 47a.

The cable 24 is thus securely locked against axial movement and could not be pulled out of the connector without the exertion of an extremely high force. At the same time, a seal is provided.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.

1 claim as my invention:

1. In an electrical connector, a hollow shell arranged to receive one end of a cable, compressible means arranged to surround a portion of said cable within said shell, and a tubular member arranged in one end of said shell to compress said compressible means into tight engagement with the cable within said shell, said compressible means comprising a generally C-shaped resilient metal member, and said tubular member having an internal surface of generally frustoconical shape arranged to wedge said C-shaped member inwardly into tight engagement with the cable within said shell, said shell having an internal shoulder therewithin at the inner end of said end portion thereof, said compressible means further comprising an annular member of elastomeric material arranged to be axially compressed between said shoulder and an inner end of said tubular member by axial movement of said tubular member, to cause the inner surface of said elastomeric annular member to be moved radially inwardly into tight engagement with said cable.

2. In an electrical connector as defined in claim 1, said tubular member being threaded into said shell.

3. In an electrical connector as defined in claim 1, an annular metal member of generally L-shaped cross section having a first wall between an end surface of said annular member of elastomeric material and said inner end of said tubular member and having a second wall surrounding one end portion of said annular member of elastomeric material, said C- shaped member having an outer diametrical dimension greater than the inner diameter of said annular metal member of L-shaped cross section. 

1. In an electrical connector, a hollow shell arranged to receive one end of a cable, compressible means arranged to surround a portion of said cable within said shell, and a tubular member arranged in one end of said shell to compress said compressible means into tight engagement with the cable within said shell, said compressible means comprising a generally Cshaped resilient metal member, and said tubular member having an internal surface of generally frustoconical shape arranged to wedge said C-shaped member inwardly into tight engagement with the cable within said shell, said shell having an internal shoulder therewithin at the inner end of said end portion thereof, said compressible means further comprising an annular member of elastomeric material arranged to be axially compressed between said shoulder and an inner end of said tubular member by axial movement of said tubular member, to cause the inner surface of said elastomeric annular member to be moved radially inwardly into tight engagement with said cable.
 2. In an electrical connector as defined in claim 1, said tubular member being threaded into said shell.
 3. In an electrical connector as defined in claim 1, an annular metal member of generally L-shaped cross section having a first wall between an end surface of said annular member of elastomeric material and said inner end of said tubular member and having a second wall surrounding one end portion of said annular member of elastomeric material, said C-shaped member having an outer diametrical dimension greater than the inner diameter of said annular metal member of L-shaped cross section. 